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The 2012 ASHS Annual Conference

9436:
Ingress of Gaseous 1-Methylcyclopropene in Tomato Fruit

Wednesday, August 1, 2012
Grand Ballroom
Xiaoqing Dong, Horticultural Sciences Department, IFAS, University of Florida, Gainesville, FL
Maricruz Ramírez-Sánchez, Horticultural Sciences Department, IFAS,, Horticultural Sciences Department, IFAS, University of Florida,, Gainesville, FL
Donald J. Huber, Horticultural Sciences Department, University of Florida, Gainesville, FL
Jing-Ping Rao, College of Horticulture, College of Horticulture, Northwest A&F University, Yangling, China
James H. Lee, Horticultural Sciences Department, IFAS, University of Florida, Gainesville, FL
Zhengke Zhang, Enviroment and Plant Protection Institute, Chinese Academy of Tropical Agricultural Sciences, Danzhou 571737, China
Recommended doses of gaseous 1-Methylcyclopropene (1-MCP, SmartFreshTM Quality System) for harvested fruits and other plant tissues have been based on analyses of external levels required to attain desired responses; however, no information is available regarding the extent and rate of 1-MCP ingress. This study addressed ingress of gaseous 1-MCP in tomato fruit exposed to 20 µL·L-1 1-MCP followed by sampling of internal atmosphere from fruit immersed in water. Harvested, unwaxed tomato fruit accumulated 1-MCP rapidly, reaching maximum values of approximately 6 to 8 µL·L-1 within 3 h at 20 °C. Internal gaseous [1-MCP] declined approximately 60% to 70% within 1 h of removal and was nearly depleted within 3 h.  1-MCP ingress was similar among fruit of all ripening stages and reduced 45% in fruit coated with commercial wax. Diffusion of gaseous 1-MCP through inert matrices (e.g., glass microfibre filters) positioned between double-flask chambers occurred rapidly (< 30 min) through dry filter paper but was completely prevented through hydrated filter paper, providing evidence that water constitutes an effective barrier to 1-MCP diffusion.  Blocking 1-MCP ingress through peduncle and style scars by application of a water barrier resulted in a 50% to 60% reduction in accumulation of internal 1-MCP, indicating that 1-MCP ingress also occurs through epidermal tissues. Fruit preloaded with 1-MCP and immersed in water for 2 h retained from 45% to 70% of 1-MCP levels measured immediately after removal from the gas, indicating that significant quantities of 1-MCP remain in gaseous form and are not rapidly sorbed or metabolized by tomato fruit tissue. Diffusion of gaseous 1-MCP occurred rapidly through baby spinach and bok choi leaves, but was nearly completely prevented in epidermal and peduncle-scar disks of tomato and other fruits. Recent work in our lab demonstrated that excised tissues of some fruits can metabolize 1-MCP through apparent wound-induced, free-radical chemistry and are not suitable models for estimating 1-MCP ingress properties. Rapid ingress of 1-MCP was also observed in tomato fruit exposed to aqueous 1-MCP.  Immersion in aqueous 1-MCP at 1 mg·L-1 for 1 or 2 min resulted in internal [1-MCP] of around 4 and 5.8 µL·L-1, respectively. Analysis of internal [1-MCP] provides another tool for investigating variable responses of different fruits/cultivars to the low levels of 1-MCP (≤1 µL·L-1) employed commercially. 1-MCP ingress is likely influenced by epidermal morphology, composition and architecture of native and applied waxes, and tissue hydration.
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